It is conventional when mounting an engine on an aircraft, whether under a wing or against the fuselage, to provide a front and a rear mounting apparatus with respect to the engine. Where the engine is a gas turbine engine, the front mounting is generally provided in the vicinity of the compressors and the rear mounting is generally provided in the vicinity of the turbines. However, other apparatuses are possible. The engine is suspended under the wings or from the tail of an aircraft by front and rear engine mounting apparatuses.
U.S. Pat. No. 6,059,227 discloses a mounting apparatus that comprises a main attachment structure, or mount block, having two load transfer links interconnecting the engine and the main attachment structure. Four bolts are provided to interconnect the aircraft pylon and the main attachment structure and thereby transfer the loads from the engine into the pylon. A standby attachment structure is provided as a fail-safe mechanism. It comprises a protrusion extending from the pylon and is arranged to sit, in use, through a slot in the main attachment structure. When it is located through the slot a pin can be inserted through an aperture in the protrusion so that the pylon and main attachment structure cannot be separated. There is a clearance around the pin in the aperture so that no load is transferred during normal usage. However, if one of the two load transfer links fails, the clearance is taken up and the load is transferred through the standby attachment structure.
One disadvantage of this apparatus is that the pin is obscured by the surrounding components. This means that it is prone to being overlooked during inspection and maintenance of the engine and mounting or assembly and / or disassembly of the engine mounting. If the pin is not inserted through the aperture in the protrusion during mounting of the engine to the aircraft pylon there is no fail-safe mechanism in the event of failure of one of the load transfer links. If the pin is not removed before the bolts during dismounting of the engine, the full weight of the engine is inadvertently transferred through the pin and the standby attachment apparatus, which may stress and damage the pin thereby requiring its replacement for full safety.
Another disadvantage of this apparatus is that the fail-safe mechanism is only effective in the event of a failure of one of the load transfer links. In the event of the failure of the main attachment structure there is no alternative load path. This is likely to result in one or both of the load transfer links being inoperative and may result in the engine becoming detached from the pylon.
A further conventional apparatus is disclosed in U.S. Pat. No. 5,275,357, which has a platform, or mount block, having three links connecting it to the engine and bolts to connect it to the aircraft pylon. Two of the links are load transfer links that are connected at one end to the engine, at the other end to the platform and at an intermediate position to the platform with a sliding connection to allow thermal expansion between the components. The third, fail-safe link is connected to the platform at one end and to the engine at the other by a pin having a clearance. Thus, during normal operation the third link is unloaded. In the event of failure of one of the two load transfer links, the clearance is taken up and the load is transferred through the third, fail-safe link.
This apparatus also is unable to provide a fail-safe mechanism in the event of failure of the platform. As with U.S. Pat. No. 6,059,227 one or both of the load transfer links may become inoperative and the engine may become detached from the pylon.